of challenges, and it won't be hard for mr. obama to see them. he just needs to look in the presidential rear-view mirror. preparing to make that inaugural walk down pennsylvania avenue for the second time, president obama will join an exclusive club within a club, one of only 17 two-term american president, all the while aware that membership can come at a price. >> i'm more than familiar with all the literature about presidential overreach in second terms. we are very cautious about that. >> reporter: historians say he's right to be cautious. >> the dangerous president is not one who feels power, it's one who feels he does not have new enough power. >> reporter: that quest for power has made many presidents stumble badly. from fdr's failed push to pack the supreme court with judges who would embrace his new deal to richard nixon. >> i am not a crook. >> reporter: whose desire to destroy his political enemies led to the watergate scandal and ultimately his resignation. >> i take full responsibility. >> reporter: then of course ronald reagan, whose second term was jeopardized by the arms for
